1. Field of the Invention
The present invention relates to a liquid ejection head that is able to eject a liquid through nozzles, a liquid ejection apparatus that allows the liquid to be ejected from the liquid ejection head, and a liquid supply apparatus and method for supplying the liquid to the liquid ejection head.
The liquid ejected from the liquid ejection head may be selected from various liquids such as ink and medical agents. If ink is used as the liquid, images can be printed by applying ink to a print medium.
2. Description of the Related Art
As liquid supply systems for liquid ejection heads, ink supply systems supplying ink to an ink jet print head (liquid ejection head) have been improved so as to adjust to increased printing speeds. However, these ink supply systems require a filter to be disposed in a channel to trap foreign matter or bubbles present in ink (liquid). Consequently, the flow of ink is subjected to a significant pressure loss in the filter portion. This prevents high-speed printing.
If the filter area is increased to reduce the pressure loss in order to solve the above problem, bubbles in a liquid chamber may remain on a bottom surface of the filter to hinder the supply of the liquid.
A proposal has thus been made that a valve be provided to close a part of the filter so as to increase the flow speed of ink only during a process of recovering a print head, to purge the bubbles (Japanese Patent Laid-Open No. 06-064183). As a similar example, a proposal has been made that a valve be provided in tight contact with the filter so as to make it easy to also increase the flow speed of ink during the process of recovering the print head to purge the bubbles (Japanese Patent Laid-Open No. 08-118672).
However, with the methods described in Japanese Patent Laid-Open Nos. 06-064183 and 08-118672, the valve provided in the vicinity of the filter complicates the structure of the system.
Further, with these conventional methods, the filter increases channel resistance during a printing operation. This makes it difficult to maintain the interior of the print head at a predetermined negative pressure. In particular, in a printing apparatus that performs a high-speed printing operation using an elongate print head (wide line head) extending across the width of a print medium, a variation in pressure increases in the vicinity of the nozzles in the print head. This makes it difficult to maintain a proper printing operation.